Valve needle for an electromagnetically actuated valve and process for manufacturing the same

ABSTRACT

The new valve needle comprises at least one valve-needle section and a valve-closure member section of the valve needle which are manufactured as one part by means of deep-drawing. To guarantee a flowing of the fuel in the direction of the valve seat, two beads are provided, for example, in the valve-needle section, while truncations are formed on the valve-closure member section having a hemispherical bowl shape. Thus, the fuel flows along on the outer periphery of the valve-needle section. The valve needle is especially suited for injection valves in fuel-injection systems of mixture-compressing internal combustion engines with externally supplied ignition.

FIELD OF THE INVENTION

The present invention is directed to a valve needle for anelectromagnetically actuated valve or to a process for manufacturing avalve needle.

BACKGROUND OF THE INVENTION

The German Patent Application No. 40 08675 already discloses a valveneedle for an electromagnetically actuated valve, which is comprised ofan armature, a valve-closure member, and a tubular connecting partjoining the armature and the, e.g., spherical valve-closure member. Theenumerated parts represent individual parts, which are each manufacturedseparately and are first joined together by means of jointing methods,e.g. laser welding. Thus, there are at least two joints (Points ofconnection). The armature in this case completely embraces theconnecting part radially and axially at least in part, since theconnecting part is secured in a longitudinal orifice passing rightthrough the armature. The connecting part, itself, also has acontinuously traversing inner longitudinal orifice, in which the fuelcan flow toward the valve-closure member and then flow out near thevalve-closure member through radially running, crosswise orificesintroduced in the inner wall of the connecting part. Therefore, the fuelfirst flows inside the valve needle and does not leave the valve needleuntil close to the valve seat.

It has also been disclosed by German Patent No. 42 30 376 to manufacturea valve needle for an electromagnetically actuated valve from aone-piece, tubular actuating part comprised of an armature section and avalve sleeve section by means of injection molding and subsequentsintering in accordance with the metal-injection-molding method (MIM).The actuating part is subsequently joined by a welding connection to avalve-closure member section. Provided in the armature section and thevalve-sleeve section is a traversing, inner longitudinal opening, inwhich fuel can flow toward the valve-closure member section and thenemerge out of the valve-sleeve section near the valve-closure membersection through crosswise orifices. Thus, in manufacturing the valveneedle using the so-called MIM method, slide molds are necessary to formthe crosswise orifices.

SUMMARY OF THE INVENTION

In contrast, the advantage of the valve needle and process according tothe present invention is that they make it possible to manufacture sucha valve needle simply and cost-effectively. This is achieved inaccordance with the present invention in that the connecting part isformed as a valve-needle section, in one piece with the valve-closuremember section, using a deep-drawing method, so that the tool used tomanufacture the deep-drawn part comprised of the valve-needle sectionand the valve-closure member section can be very simple in design.Transverse slide molds for producing crosswise orifices in thevalve-needle section are not needed, since the fuel flows outside of thevalve-needle section.

What is also advantageous during the deep-drawing process is that acomparatively simple flat blank of a suitable deep-drawing sheet metalcan be used as starting material.

The deep-drawn part is inserted in an inner through-hole of an armatureand permanently joined to the armature, e.g., by means of welded seams.Thus, the valve needle according to the present invention merely has atwo-part design.

For example, two axially running flow channels inside the armatureensure an unhindered flow of fuel in the direction of the valve seat.The fuel emerging from the flow channels can flow along the periphery ofthe valve-needle section without being diverted.

What is advantageous is that beads provided in the valve-needle section,which are used to form the flow channels inside the armature, are ableto be produced free of burrs, so that contrary to crosswise orificesafflicted with burrs in manufacturing processes known heretofore, noreworking is necessary. Moreover, it is especially advantageous thatparticles carried along in the fuel or washed-in dirt can settle in thecup-shaped deep-drawn part, so that leakage caused by blockage on thevalve seat can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a fuel-injection valve having a needle according toan embodiment of the present invention.

FIG. 2 illustrates a plan view of a valve needle according to thepresent invention.

FIG. 3 illustrates a first sectional view of the valve needle accordingto the present invention, along the line III--III of FIG. 2.

FIG. 4 illustrates a second sectional view of the valve needle accordingto the present invention, along the line IV--IV of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The electromagnetically actuated valve depicted by way of example inFIG. 1 in the form of an injection valve for fuel-injection systems ofmixture-compressing internal combustion engines with externally suppliedignition has a tubular core 2, which has, for example, a constant outerdiameter over its entire length, is surrounded by a solenoid coil 1, andis used as a fuel intake connection. A coil form 3 that is stepped inthe radial direction accommodates a winding of the solenoid coil 1 and,in conjunction with the core 2, renders possible a compact design of theinjection valve in the area of the solenoid coil 1.

Concentrically to a longitudinal valve axis 10, a tubular, metallicadapter part 12 is imperviously joined, for example by means of welding,to a lower core end 9 of the core 2 and axially surrounds the core end 9in part. A tubular valveseat support 16, which, for example, is fixed tothe adapter part 12, extends downstream from the coil form 3 and theadapter part 12. A longitudinal bore 17, which is formed concentricallyto the longitudinal valve axis 10, runs in the valve-seat support 16.

A valve needle 18 in according to the present invention having adeep-drawn, tubular valve-needle section 19 is arranged in thelongitudinal bore 17. Provided at the downstream end 23 of thevalve-needle section 19 is a valve-closure member section 24, which hasat least a partially spherical outer contour, is designed in one piecewith the valve-needle section 19, and has five truncations (flattendarea) 25 provided on its periphery, for example, to allow the fuel toflow past.

The injection valve is actuated electromagnetically in a generally knownway. The electromagnetic circuit comprising the solenoid coil 1, thecore 2, and an armature 27 is used to axially move the valve needle 18and, thus, to open the injection valve opposite the spring tension of arestoring spring 26, or to close the injection valve. The tubulararmature 27 is permanently attached, for example, by two welded seams 28to an end 20 of the valve-needle section 19 inserted in the armature 27and facing away from the valve-closure member section 24, and is alignedto the core 2. Together with the deep-drawn part 31 comprised of thevalve-needle section 19 and the valve-closure member section 24 formeddownstream, the armature 27 forms the valve needle 18 serving as theactuating part. A cylindrical valve-seat member 29, which has a fixedvalve seat 30, is imperviously installed by means of welding in thedownstream end of the valve-seat support 16 facing the core 2, in thelongitudinal bore 17. A guide orifice 32 of the valve-seat member 29 isused to guide the valve-closure member section 24 during the axialmovement of the valve needle 18 along the longitudinal valve axis 10.The valve-closure member section 24 of the valve needle 18 having aspherical outer contour interacts with the valve seat 30 of thevalve-seat member 29 that tapers frustoconically in the direction offlow. At its front end facing away from the valve-closure member section24, the valve-seat member 29 is permanently and imperviously joined by,e.g., a laser-produced welded seam to an apertured spray disk 34 havinga pot shape, for example. At least one, for example four spray-dischargeorifices 39 are provided in the apertured spray disk 34 by means oferosion or punching.

The insertion depth of the valve-seat member 29 with the apertured spraydisk 34 determines the magnitude of the lift of the valve needle 18. Theend position of the valve needle 18, given an unexcited solenoid coil 1,is stipulated by the contact making of the valve-closure member section24 on the valve seat 30 of the valve-closure member 29, while the otherend position of the valve needle 18, given an excited solenoid coil 1,results from the contact making (seating) of the armature 27 at the coreend 9.

The solenoid coil 1 is surrounded by at least one conductive element 45,designed, for example, as a clip (bracket) and used as a ferromagneticelement, which surrounds the solenoid coil 1 in the circumferentialdirection at least partially and abuts with its one end on the core 2and with its other end on the valve-seat support 16 and is able to bejoined to said valve-seat support 16, for example, by means of welding,soldering, or bonding. An adjustment sleeve 48 inserted into a flow bore46 of the core 2 running concentrically to the longitudinal valve axis10 is used to adjust the initial spring tensioning of the restoringspring 26, which adjoins the adjustment sleeve 48 and is braced, inturn, with its opposite side, against an upstream front end 49 of thevalve-needle section 19 in an inner through-hole 50 of the tubulararmature 27.

The injection valve is largely enclosed by a plastic extrusion coat 51,which, emanating from the core 2, extends in the axial direction via thesolenoid coil 1 and the at least one conductive element 45 up to thevalve-seat support 16, the at least one conductive element 45 beingcompletely covered axially and in the circumferential direction. Alsobelonging to this plastic extrusion coat 51 is, for example, anelectrical plug connector 52 that is extruded on as well.

A valve needle 18, according to the exemplary embodiment depicted inFIG. 1 is also illustrated in a plan view in FIG. 2. FIGS. 3 and 4 aresectional views along the line III--III or IV--IV in FIG. 2 andillustrate two exemplary embodiments of valve needles 18, which differfrom one another only in the area of the valve-closure member sections24. On the basis of these three FIGS., the design of the valve needle 18or the process for its manufacture according to the present inventionshall be elucidated in the following.

In a first process step, a flat blank made of a suitable deep-drawnsheet metal, e.g. of austenitic or ferritic steel, is formed into acup-shaped part. This is a deep-drawing process, a translationaltension-compression shaping (form design) process. The deep-drawingprocess is especially suited, as in the present case, for cold-forminghollow parts that are open to one side, rotationally symmetric, and havea constant wall thickness. In accordance with the design of thedeep-drawing tool (bottom die, stamp), the cup-shaped deep-drawn part 31comprised of the valve-needle section 19 and the valve-closure membersection 24 can already be given a very exact form and size. Thedeep-drawn part 31 shown in FIG. 4 is able to be produced more simplythan the deep-drawn part 31 shown in FIG. 3 using the deep-drawingprocess, since it has a constant inside diameter up to a valve-closuremember section 24 having, e.g., a hemispherical bowl shape. On the otherhand, the deep-drawing of the deep-drawn part 31 shown in FIG. 3 causesthe inside diameter of the valve-needle section 19 and, thus, also theoutside diameter as well to be enlarged in the vicinity of thevalve-closure member section 24, so that, spatially, the outside contourof the valve-closure member section 24 has more than one hemisphere.

Provided in a following process step on the deep-drawn part 31 in thevicinity of the valve-closure member section 24 on its outer contourare, for example, five truncations 25, which are disposed equidistantlyfrom one another and facilitate the flowing past of fuel in the guideorifice 32 of the valve-seat member 29 up to the valve seat 30. Thesetruncations 25 extend at least up to the largest cross-section of thevalve-closure member section 24, allowing a fuel flow to initiallymaterialize, and do not reach up to the plane of contact (tangency) ofthe valve-closure member section 24 on the valve seat 30. Thesetruncations 25 are premolded, e.g., by means of upsetting (heading) orstamping. These processes are translational compression shapingprocesses, in which, therefore, the tool essentially moves linearly. Interms of one particular case, substantially radially acting stampingforces cause a slight displacement of material toward a deep-drawingpartial longitudinal axis 60, which, in the installed state of the valveneedle 18, coincides with the longitudinal valve axis 10.

The valve-needle section 19 is subsequently provided at its end 20,which faces away from the valve-closure member section 24 and is securedlater in the inner through-hole 50 of the armature 27, with, forexample, two axially running V-shaped beads 61. These beads 61 are alsopremolded, e.g., by means of stamping so as to be free of burrs and, infact, at least at such a length, that they project downstream out of thelater installed armature 27. In the installed state of the deep-drawnpart 31 in the armature 27, the beads 61 represent the flow channels 63,which are delimited by the inner wall of the armature 27 and by thecontour of the beads 61 of the valve-needle section 19. Thus, comingfrom the flow bore 46 in the core 2, the fuel arrives at the armature 27and enters into its inner through-hole 50 up to the front end 49 of thevalve-needle section 19. On the one hand, fuel flows, at least in thecase of immediate initial operation, into the inside of the cup-shapeddeep-drawn part 31 and, mainly into both flow channels 63, which beginat the front end 49 and through which the fuel is now directed. In thevicinity of the end of the armature 27 facing the valve-closure membersection 24, the fuel flows out of the flow channels 63 again and flowsat least partially as a wall film of the deep-drawn part 31 to the valveseat 30. Thus, the fuel flow up to the valve seat 30 is completelyguaranteed without longitudinal slits or crosswise orifices in thevalve-needle section 19. The two last described process steps can alsobe carried out perfectly well in reverse chronological sequence, thusfirst premolding beads 61 and then applying the truncations 25, or becarried out simultaneously.

The valve-closure member section 24 undergoes a surface treatment in anext process step. This surface treatment can be realized as ahard-material coating with a thin, wear-resistant hard chromium layer.Other ideal coating materials are, for example, titanium carbide,titanium nitride or tungsten carbide. To apply the coating through thefine deposition of hard materials out of the gas phase, vapor-depositionprocesses, such as the so-called CVD (chemical vapor deposition)--or PVD(physical vapor deposition) processes have succeeded. A correspondingfine machining (e.g., lapping) of the valve-closure member section 24having a partially spherical outer contour must then still follow whenthe surface quality does not yet have the quality stipulated for avalve-closure member.

A last process step for manufacturing the valve needle 18 follows. Thedeep-drawn part 31 is inserted into the inner through-hole 50 of thearmature 27 and permanently fixed to the same. The permanent connectionis able to be achieved, e.g., by applying two laser-produced weldedseams 28 from the outer periphery of the armature 27. It is advantageousthat the welded seams 28 oppose one another exactly and are onlyprovided where the deep-drawn part 31 also contacts the inner wall ofthe armature 27, thus outside of the beads 61. The process according tothe present invention for manufacturing a valve needle 18 has theadvantage that the valve needle 18 is able to be fabricated without anycutting or burr-producing process steps.

All process steps described here that are required after thedeep-drawing process do not necessarily have to be carried out in thespecified chronological sequence. It is equally possible for theindividual process steps to take place, at least in part, in a differentchronological sequence or simultaneously.

What is claimed is:
 1. A valve needle for an electromagneticallyactuated valve, the actuated valve having a core, a solenoid coil and afixed valve seat, the valve needle comprising:an armature; a valveclosure member section interacting with the fixed valve seat; a valveneedle section connecting the armature to the valve closure membersection; wherein the valve needle section and the valve closure membersection are formed from a single blank, the single blank being formedvia deep-drawing, and the valve needle section and the valve closuremember section forming a single element, wherein the single element hasfirst and second ends, the first end being open and the second end beingclosed, and the valve closure member section is formed at the secondend.
 2. The valve needle as recited in claim 1, wherein theelectromagnetically actuated valve includes an injection valve for afuel-injection system of an internal combustion engine.
 3. The valveneedle as recited in claim 1, wherein the single element has anelongated cup shape, and the valve needle section has a tubular shape.4. The valve needle as recited in claim 1, wherein the valve closuremember section has a hemispherical-bowl shape.
 5. The valve needle asrecited in claim 3, wherein the first end is attached to the armature byat least one welded seam.
 6. A valve needle for an electromagneticallyactuated valve, the actuated valve having a core, a solenoid coil and afixed valve seat, the valve needle comprising:an armature; a valveclosure member section interacting with the fixed valve seat; a valveneedle section connecting the armature to the valve closure membersection, the valve needle section and the valve closure member sectionbeing formed from a single blank, the single blank being formed viadeep-drawing; and at least one bead molded from an outer periphery ofthe valve needle section at a first end of the valve needle section, thefirst end facing away from the valve closure member section.
 7. Thevalve needle as recited in claim 6, wherein at least one bead of thevalve needle section has a V-shape and is elongated in an axialdirection.
 8. The valve needle as recited in claim 7, wherein thearmature includes a through-hole for receiving the single element. 9.The valve needle as recited in claim 8, wherein when the single elementis inserted in the through-hole and the at least one bead forms at leastone axially running flow channel, the at least one flow channel beingformed inside the armature.
 10. A process for manufacturing a valveneedle having an armature, the process comprising the steps of:shaping asingle lank via a deep-drawing procedure to form a single element with avalve needle section and a valve closure member section, the valveclosure member section having an outer periphery and the valve needlesection having a first end facing away from the valve closure membersection; placing at least one truncation on the outer periphery of thevalve closure member section via at least one of an upsetting procedureand a stamping procedure; molding at least one bead at the first end ofthe valve needle section; surface-treating the valve closure membersection; and connecting the armature and the valve needle section. 11.The process as recited in claim 10, wherein the at least one bead ismolded via a stamping procedure.
 12. The process as recited in claim 10,wherein the step of surface-treating includes applying at least onelayer.
 13. The process as recited in claim 12, wherein the at least onelayer is applied by a chemical vapor deposition process.
 14. The processas recited in claim 12, wherein the at least one layer is applied by aphysical vapor deposition process.
 15. The process as recited in claim12, wherein the step of connecting includes forming a permanentattachment of the armature and the valve-needle section.
 16. The processas recited in claim 10, wherein the valve closure member section and thevalve needle section form a single element, the single element having anelongated cup shape and the valve needle section having a tubular shape.17. The process as recited in claim 10, wherein the valve closure membersection has a hemispherical-bowl shape.
 18. The process as recited inclaim 10, wherein the at least one bead of the valve needle section hasa V-shape and is elongated in an axial direction.
 19. The process asrecited in claim 16, wherein the armature includes a through-hole forreceiving the single element.
 20. The process as recited in claim 19,wherein when the single element is inserted in the through-hole, the atleast one bead forms at least one axially running flow channel, the atleast one flow channel being formed inside the armature.